Method of protecting machinery from corrosion by acid-reacting substances tending to accumulate in lubricating oils



United States Patent METHOD 0]? PROTECTIBIG MACHINERY FROM CORROSION BY ACID-REACTING SUBSTANCES TENDING T0 ACCUMULATE IN LUBRICATING OILS Abraham Shapiro, Los Angeles, 'Calif., assignor to Socony Mobil Oil Company, Inc., New York, N.Y., a corporation of New York No Drawing. Filed July 7, 1958, Ser. No. 746,675 4 Claims. (Cl. 252-40) This invention relates to protection of engines and other machinery from the corrosi e effects of acid-reacting substances which tend to accumulate in lubricating oils.

The problem is a familiar one in internal-combustion engines which employ fuels of high sulfur content. Sulrfur dioxide and other acidic oxidation products are produced in the cylinders, and some of the acidic material finds its way into the crankcase oil with the result that bearings and other parts are exposed to corrosion.

Various oil-soluble basic substances have been added to lubricating oils for the purpose (among others) of neutralizing acid-reacting substances which tend to contaminate the oils. These have functioned satisfactorily when the quantity of acid material is small, as in gasoline engines employing fuels of low sulfur content. But when highly sulfurous fuels are used, any reasonable amount of basic additive in the lubricating oil becomes neutralized and ineifective long before the oil is otherwise ready for replacement.

Another procedure, common in marine usage, has been to periodically or continuously remove oil from the crankcase, agitate it with water, separate the oil fromthe water in a centrifuge, and return the washed oil to the crankcase. This method prevents the oil from becoming more than mildly corrosive but it does not completely prevent corrosion.

Heretotfore, these two procedures have been incompatible with one another. The oil-soluble basic substances which have been added to lubricating oils, or their sulfi-tes and similar salts, have acted as emulsifying agents. Consequently, when oils containing them have been agitated with water, emulsions have formed which cannot be separated by centrifugal treatment or other methods practical for use by operators of engines. For this reason it has been customary to omit basic additives from lubricating oils which are to be washed with water.

I have discovered that the two procedures can be combined if a particular basic material or its components are employed in a lubricating oil. The material is the fraction of nitrogen bases from coal tar having a boiling range of 240 to 265 C. This fraction is soluble in oil and insoluble in water, it is adequately stable with respect to oxidation, it combines with sulfur dioxide and other corrosive acid substances to form salts which are soluble in water and have only limited solubility in oil, and it has no tendency to stabilize emulsions of lubricating oil and water. It is, therefore, extremely effective in neutralizing corrosive substances and transferring them from the oil to the wash water.

It is necessary to exclude from the lubricating oil the nitrogen bases which act as emulsifying agents or which are subject to oxidation or other chemical changes whereby emulsifying agents or gummy substances are formed.

The above-described material, employed as an additive for lubricating oils, also provides a solution for problems encountered with oils which are not intentionally washed with water but which are subject to being brought into contact with water in other ways. For example, crankcase oils may be contaminated with water which con- 2,996,454 Patented Aug. 15, 1961 ice denses from the combustion products or by water which leaks from the cooling systems of engines. The previously employed basic additives have caused this water to emulsify with the oil. The additive herein disclosed allows the accidentally introduced water to separate from the oil, thus permitting continued use of oil which otherwise would require early replacement.

The fraction consists essentially of the methylquinolines, the methylisoquinolines, and isoquinoline. The various members of this group of chemical compounds and their mixtures are all capable of serving the purposes set forth herein. But quinoline itself, being a water-soluble sub stance, is not suitable for use.

In the processing of coal tar it is usual to treat the tar or a distillate fraction of it with dilute sulfuric acid to extract basic constituents, to free the bases from the resulting aqueous solution by addition of caustic soda or other alkali, and to distill the mixture of free bases to obtain products such as quinoline. The separation of quinoline in this manner yields as a by-product a distillation residue having an initial boiling point of about 240 C.

This residue consists mainly of methylquinolines, methylisoquinolines, and isoquinoline but, in the form available in commerce, it also contains tarry substances which make it unsuitable for use as an additive for lubricating oils. By subjecting the commercially available residue to vacuum distillation at a pressure of not more than about 0.1 atmosphere to produce an overhead fraction with a boiling range of 240 to 265 C. and discarding the still base (which amounts to about 10% of the original material), a substance fully satisfactory for blending with lubricating oil is obtained.

By parallel procedure nitrogen-base fractions can be prepared from petroleum distillates, but these are complex, malodorous mixtures that are rich in constituents which oxidize readily to produce gummy substances. Therefore the nitrogen bases from petroleum are not desirable for the purposes set forth herein.

Small amounts of the additive herein disclosed do not adversely aifect any of the desired properties of lubricating oils. As the proportion of additive is increased, the firs-t lubricating-oil property to suffer is the flash point. Use of 4% of the additive brings the flash point of ordinary lubricants down to about 350 F. (Cleveland open cup), which is the minimum most often specified for crankcase oils. The additive also tends to decrease the I viscosity of an oil, at least as measured at 100 F., but

this can be readily counteracted by use of a more viscous lubricant stock.

If desired, the tendency of the material to depress flash points of oils can be ameliorated by distilling 01f the more volatile components and using the less volatile portion as the additive. The more volatile portion, consisting mainly of isoquinoline or of a mixture of isoquinoline and quinaldine, need not be discarded but can be used in oils in which lower flash points are permissible or in which lesser amounts of the additive are needed. I have found that, merely by heating the material in an open container to temperatures of 450 to 500 F. until the volume is reduced to of the original, the flash points of oils compounded with 4% of additive are increased by about 20 F.

By reducing the volatility of the additive it is possible to compound oils having considerably more than 4% of the additive even when a minimum flash point of 350 F. is specified. When the flash point is not a critical property no definite maximum for the proportion of additive can be stated, for very large amounts can be used without diminishing viscosity and lubricity to the points where an oil ceases to be useful as a lubricant. In oils which are used in severely acid conditions without periodic washing, the prolongation of the period of protection from acid may more than compensate for a moderate sacrifice of lubricant properties.

If plain water or sea water is used to wash the oil, the

present invention was compounded with 1% of the fraction of coal-tar bases having a boiling range of 240 to 265 C. and 99% of a mineral lubricating oil having viscosities of 1275 and 101 S.S.U at 100 F. and 210 F.

neutralized nitrogen bases are removed from the oil and 5 repectively and a pH of 4.7. The resulting composition discarded with the water. Consequently, the proportion had viscosities of 929 and 85.8 at 100 F. and 210 F. of additive in the oil keeps diminishing. It continues to respectively and a pH of 5.5. This example was used in protect bearings and other parts from corrosion until it a 6-cylinder Buda engine employing as fuel a gasoline of falls below about 0.1%, but when that occurs more of the 0.65% sulfur content for a test run of 200 hours. The additive should be put in the oil. 1 test indicated that use of the additive had no observable Operators of engines cannot be expected to have facilieffect upon lubricity of the oil, that it did not lead to ties for determining the percentage of nitrogen bases is formation of undesirable deposits on metallic parts, and an oil, but an operator with a normal olfactory sense that it was successful in neutralizing acid oxidation prodcan make a rough but adequate determination by smellucts under actual operating conditions. ing the washed and separated oil; it the characteristics I claim as my invention: quinoline-like odor is absent or very weak, the content of 1- In a method of protecting machinery from corroadditive in the oil should be replenished. Another methsion by acid-reacting substances tending to accumulate od is to shake the used, unwashed oil with distilled water in the oil employed to lubricate said machinery which and to test the water with litmus, and to replenish the adincludes washing said oil by agitation with an aqueous ditive in the washed and separated oil if an acid reaction liquid, Separating the Washed Oil from Said aqeous q is noted. The latter test does not necessarily indicate the and returning the washed and separated oil to said mapresence or absence of nitrogen bases, but it can be aschinery, the improvement which comprises: maintaining sumed that an oil which does not test acid with litmus in said oil at least 0.1 percent by weight of a mixture of is substantially noncorrosive either because of low conorganic basic substances derived by extracting bases from centration of acidic substances or because of the presence coal tar with an aqueous acid solution, subsequently of enough basic material to effect adequate neutralization. alkalizing said solution to free organic bases therefrom,

Maintenance of a suflicient quantity of the additive in and distilling the free bases to obtain a fraction having an an oil can also be achieved, in most cases more economiinitial boiling point of at least 240" C. and an end point cally, by employing wash water which has been alkalized of 265 C. by addition of up to 1.0% of caustic soda or its equiva- 2. A method as described in claim 1, wherein said aquelent. When this is done the alkaline water decomposes ous li uid is approximately neutral and said quantity of f Salts of the nitrogfin bases, and the free bases i said basic material is maintained in said oil by periodic oll'soluble and water'msoluble) to the lubrlcaimg addition of further amounts of said material to said oil. oil and continue to protect metallic parts from corrosion. A method as described in claim 1, wherein said I have hh that when ohs ,cohtalhmg, h' quantity of said basic material is maintained in said oil by closed add tive are saturated with sulfur dioxide, agitated making said aqueous liquid sufficiently alkaline to wlth .alkahhe Wathr and separated .from h h by compose salts of said basic material but not more alkaline centrifugal treatment, the washed oils are indistinguishth n on ercent a ueous solufon f a d able with regard to pH and other properties from the a 6p h d g 1 o us so same oils which had not been exposed to sulfur dioxide. 40 n a 0 o Protectmg mahhmery from 9' The table shows representative properties of four dif- S1011 h acld'reactmg subsiances hendmg 9 h p ferent mineral lubricating-oil stocks and, as specific examthe oh h h h mhchmehy Whlch ples of lubricants compounded according to this invenclhdes washhlg Sald Oh by *g h an aqueou's tion, oils prepared from those stocks by addition of 1% separahng thh washed 011 from said aqueous hquldr and f the f ti f coaptar nitrogen bases having and returning the washed and separated oil to said ma. a boiling range of 240 to 265 C. In the table prOporchinery, the improvement which comprises: maintaining tions of the additive are expressed as percentages by in said oil at least 0.1 percent by wei ht of a mixture of weight with respect to the total oil, flash points and pour organic basic substances derived by extracting bases from points are in degrees Fahrenheit, and viscosities are in coal tar with an aqueous acid solution, subsequently alkalseconds Saybolt Universal. 5o izing said solution to free organic bases therefrom, and

Stock A Stock B Stock 0 Stock D Percent additive" 0 1 0 1 4 0 1 4 0 1 4 Gravity, A.P.I 26.8 27.2 26.2 26.4 26.4 25.0 25.9 25.7 24.3 25.0 25.0 23.7 Color, A.S.T.M L45 L6 7 L5 D7 L8 7 D7 8 7 L8 D8 Flash, 0.0.0..... 425 395 340 440 395 340 460 400 345 430 410 355 Pour point +10 +15 +15 -5 +15 +15 +15 +15 +10 +15 +15 +5 62.0 61.4 76.0 77.9 77.2 93.9 96.2 96.0 117.0 118.9 117.5 Visc. index 82 92 93 69 88 97 86 86 84 Neutralization N0 .01 .03 .02 .01 .03 .03 .03 .03 .01 .03 .05 Carbonresidue--- .15 .21 .23 .24 .25 .31 .35 .35 .42 .69 .37 .49 n 8.1 8.2 8.1 8.4 6.2 8.0 8.5 8.0 8.7

otal base No 0.18 0.8 0.21 0.7 0.04 0.24 1.0 0.15 0.7

In addition to the properties reported in the table, core5 distilling the free bases to obtain a fraction having a boilrosion tests were run on Stock C and the compounded ing range of 240 C. to 165 C. oils prepared from it, by immersing polished metal strips in the oils for twenty-four hours at a temperature of References Cted the file of this Pawnt F. The steel and aluminum strips showed no change in UNITED STATES PATENTS py of the pp ow v r. was rnishedby the 70 1,768,910 11mg July 1, 1930 011 which contained no additive and was left brlght by 2,136,788 Fairlie Nov. 15 1938 the oils which did contain the additive. 2,441,949 Sexton et a] May 19 1948 Another specific example of the lubricating oils of the 2,647,824 Jones et a1. Aug. 4, 1953 Patent No. 2 '9 96ifi54 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Abraham Shapiro It is hereby certified that error appears in -the above numbered patentrrequiring correction and that the said Letters Patent should read as corrected below Column 3, line 12, for "is" read in "line l5, for "characteristicsread characteristic --5 line 35., for "he? xjead the column 4L line 5 for "repectivelW- read respectively line 66 for ,"'l65 C. read 265 C.

Signed and sealed this 27th day of March 1962.

SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents August 15, 1961 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,996,454 August 15, 1961 Abraham Shapiro It is hereby certified that error appears in ,the above numbered patentrequiring correction and that the said Letters Patent should read as corrected below Column 3, line 12, for "is" read in line 15, for "characteristics" read characteristic line 35,, for "he? read the column '4, line 5, for "repectively" read respectively line 66 for 165 C'." read 265 C.

Signed and sealed this 27th day of March 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID L. LADD Atteeting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.1 2,996,454 A A August 15, 1961 7 Abraham Shapiro It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 12, for "is" read in line 15, for "characteristics" read characteristic 'line 35,, for "he? read the column '4, line 5, for "repectively" read respectively line 66 for- "165 0." read 265 C.

Signed and sealed this 27th day of March 1962.

(SEAL) Attcst:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1.IN A METHOD OF PROTECTING MACHINERY FROM CORROSION BY ACID-REACTING SUBSTANCES TENDING TO ACCUMULATE IN THE OIL EMPLOYED TO LUBRICATE SAID MACHINERY WHICH INCLUDES WASHING SAID OIL BY AGITATION WITH AN AQUEOUS LIQUID, SEPARATING THE WASHED OIL FROM SAID AQUEOUS LIQUID, AND RETURNING THE WASHED AND SEPARATED OIL TO SAID MACHINERY, THE IMPROVEMENT WHICH COMPRISES: MAINTAINING IN SAID OIL AT LEAST 0.1 PERCENT BY WEIGHT OF A MIXTURE OF ORGANIC BASIC SUBSTANCES DERIVED BY EXTRACTING BASES FROM COAL TAR WITH AN AQUEOUS ACID SOLUTION, SUBSEQUENTLY ALKALIZING SAID SOLUTION TO FREE ORGANIC BASES THEREFROM, AND DISTILLING THE FREE BASES TO OBTAIN A FRACTION HAVING AN INITIAL BOILING POINT OF AT LEAST 240*C. AND AN END POINT OF 265*C. 